u/Fair_Ad7063

I'm creating a campaign where the party is invited by a revered archaeologist to join him as muscle on an expedition to chart a new underground cave system that has been discovered due to an earthquake. Hes offering a share of all the treasure they find along the way and once they reach the end of the cave they discover an ancient abandoned city where people used to worship a dracolich. Im struggling to come up with ideas for encounters and interesting things to add to expedition through the caves and the eventual exploration through the newly discovered city. Any ideas or advice would be great thank!